title: A LOV-domain-mediated blue-light-activated adenylate (adenylyl) cyclase from the cyanobacterium Microcoleus chthonoplastes PCC 7420.
abstract: Genome screening of the cyanobacterium Microcoleus chthonoplastes PCC 7420 identified a gene encoding a protein (483 amino acids, 54.2 kDa in size) characteristic of a BL (blue light)-regulated adenylate (adenylyl) cyclase function. The photoreceptive part showed signatures of a LOV (light, oxygen, voltage) domain. The gene product, mPAC (Microcoleus photoactivated adenylate cyclase), exhibited the LOV-specific three-peaked absorption band (λmax=450 nm) and underwent conversion into the photoadduct form (λmax=390 nm) upon BL-irradiation. The lifetime for thermal recovery into the parent state was determined as 16 s at 20°C (25 s at 11°C). The adenylate cyclase function showed a constitutive activity (in the dark) that was in-vitro-amplified by a factor of 30 under BL-irradiation. Turnover of the purified protein at saturating light and pH 8 is estimated to 1 cAMP/mPAC per s at 25°C (2 cAMP/mPAC per s at 35°C). The lifetime of light-activated cAMP production after a BL flash was ~14 s at 20°C. The temperature optimum was determined to 35°C and the pH optimum to 8.0. The value for half-maximal activating light intensity is 6 W/m2 (at 35°C). A comparison of mPAC and the BLUF (BL using FAD) protein bPAC (Beggiatoa PAC), as purified proteins and expressed in Xenopus laevis oocytes, yielded higher constitutive activity for mPAC in the dark, but also when illuminated with BL.
authors.affiliation: *Max-Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Mülheim, Germany.
authors.forename: Sarah
authors.initials: S
authors.lastname: Raffelberg
authors.forename: Linzhu
authors.initials: L
authors.lastname: Wang
authors.forename: Shiqiang
authors.initials: S
authors.lastname: Gao
authors.forename: Aba
authors.initials: A
authors.lastname: Losi
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Gärtner
authors.forename: Georg
authors.initials: G
authors.lastname: Nagel
mesh_terms: D000262:Adenylyl Cyclases / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D000458:Cyanobacteria / Q000201:enzymology* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008027:Light; D009865:Oocytes / Q000378:metabolism; D017434:Protein Structure, Tertiary; D013696:Temperature; D014982:Xenopus laevis
chemical_list: D001426:Bacterial Proteins; D000262:Adenylyl Cyclases